1. Field of the Invention
This invention resides in the field of slab gel electrophoresis and particularly in the design and construction of cassettes for holding a slab gel during electrophoresis.
2. Description of the Prior Art
Electrophoresis is widely used in both the clinical laboratory and the research laboratory as a rapid and effective separation process for analyzing complex, biologically derived mixtures. One of the media in which electrophoresis is commonly performed is a slab gel, which permits the simultaneous analysis of several samples by dividing the slab into lanes and using one lane for each sample. The use of a slab gel in this manner affords not only speed and an efficient use of time, but also eliminates many of the problems that commonly arise when separate procedures are performed on each of a series of samples, such as nonuniformity due to variations in gel quality and operating conditions, and the risk of operator error. The electropherograms produced in slab gels can be read and interpreted visually, allowing the user to readily identify the components present in the sample by observing the locations of the bands.
Slab gels are typically retained in cassettes that can be readily inserted in, and removed from, an electrophoresis cell which contains the components needed for imposing an electric current across the gel. A cassette is typically constructed from two plastic plates joined together with appropriate spacers to form a gap of specified width between the plates for the gel, with sealing features to prevent leakage of the gel-forming monomer mixture during gel casting as well as the gel itself during electrophoresis. In many cases, gels are pre-cast in cassettes by manufacturers to a variety of specifications. In others, users cast their own gels in cassettes immediately prior to use. Whether the gel is pre-cast or not, the removal of the gel from the cassette for staining, recordation, quantification, or other procedures following the separation requires the cassette to be opened to provide access to the gel. The opening of the cassette can be a delicate operation since it involves breaking the seals around the gel and separating the plates without damaging or distorting the gel. The seals must therefore be capable of being opened or broken and yet provide a liquid-tight seal along the edges of the two plates to assure product uniformity and reliability. Ultrasonic welding is often used as a means of joining the plates together since the weld is readily broken when the gel is ready for removal. Ultrasonic welding is a delicate process however and requires a careful balance between achieving an effective seal and allowing the user to break the seal when the separation is completed without damaging the plates themselves which often results in damage to the gel.